Abstract

A major resource holder (MRH) and a major integrated service provider conducted the first point-source/point-receiver (single-sensor) onshore seismic survey in the Middle East in early 2004 as a pilot study under a Joint Technology Agreement. The study investigated and subsequently determined that single-sensor acquisition and processing techniques could improve seismic imaging and reservoir characterization of the onshore Minagish field, for which previous attempts to derive reservoir properties from seismic data had been largely unsuccessful. The key to success was the ability of single sensor acquisition and processing technology to effectively remove noise (Ozbek, 2000) and preserve signal fidelity and high frequencies in the prestack data.

Minagish Field setting and geophysical background

Kuwait contributes approximately 9% of the world's daily output of oil. The Minagish Field, discovered in 1959 in southwestern Kuwait, is one of the country's main producing fields. It was selected for the pilot study to address multiple development and exploration objectives, one of which was to improve the resolution of the seismic time-lapse response across the producing oolitic reservoir. Fluid movements in the reservoir are complex, with water influx in higher permeability layers overriding oil.

A 48-fold 3D survey was acquired over the Minagish Field in 1996. In 1998, a seismic crew returned to acquire a trial 4D survey over a 24-km area centered on the main injector well. The 1998 data and 1996 baseline were reprocessed using the day's most advanced seismic data processing techniques. However, while core samples and log analyses predicted that a 4D effect should be observable, the 1998 4D study found that possible 4D effects observed around the main injector well had similar amplitude to the ambient noise.

Within the survey area, environmental, non-repeatable noise generators such as gas flares and water injection plants, coupled with seismic-generated noise such as air blast, ground roll, and multiples, contribute to the severe contamination of the raw seismic records.

Tests have shown how increasing receiver (and source) array length degrades signal fidelity and limits bandwidth (Figure 1) due to the aliasing of signal and noise energy.

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